An attempt to recreate the circumstances of the transition between pages in galaxy.
To start a transition, type goToPage(pages.$NAME) in the browser console, where $NAME is one of:
BaseLoginAppShowOrgAppListOrgUserList
To finish it, type finishTransition().
The idea is to pad out the HTML and write the CSS to prove that a given layout works, both normally, and during a transition.
The next step would be to expand this app to actually run transitions via CSSTransitionGroup or something. But that seems like a distinct next step once we actually are sure our basic layout works.